drm/i915/dsb: Define more DSB registers

Add definitions for more DSB registers. Less annoying spec
trawling when working on the DSB code.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230118163040.29808-2-ville.syrjala@linux.intel.com


Reviewed-by: Animesh Manna <animesh.manna@intel.com>